LonWorks In Brief (Local Operating Networks)

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LonWorks In Brief(Local Operating Networks)

• LILI MA
• 02/07/2002

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Outline

• Why LonWorks?
• Major LonWorks Elements
• Comparison with CAN Bus

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Open Control Network

• Open
• Intelligent devices communicate directly with
  each other
• No supervisory device polls information from
  devices and retransmit the information to other
  devices
• No supervisory device is responsible for
  system-wide control algorithms
• Control Networks Requirements
• Frequent, reliable, secure communications between
  devices
• Short message formats for information being
  passed
• Peer-to-Peer functionality for every device
• Low cost devices

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What is LonWorks?

• LonWorks is a universal control-networking
  platform that allows us to inexpensively
  implement a reliable distributed control network
• It is the solution when you are seeking open
  interoperable control products and systems
• It was introduced in 1991 by Echelon Corporation
  and is supported by more than 4,000 companies
  worldwide

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Major Elements of LonWorks

• LonWorks Protocol (LonTalk Protocol)
• Neuron Chips
• Transceivers

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LonWorks Protocol

• Is the heart of LonWorks
• Designed to follow the ISO standard "Open Systems
  Interconnection" Reference Model
• Designed for Control Networks specific
  requirements
• Layered, packet-based, peer-to-peer protocol
• Channel Types
• Media Access Control
• Addressing
• Message Services
• Network Variables
• Limits
• Interoperability
• Two FAQ

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Protocol - Channel

• Channel
• a specific physical communication medium (such as
  twisted pair) to which a group of LonWorks
  devices are attached by transceivers specific to
  that medium.
• Each type of channel has different
  characteristics in terms of
• Number of devices attached
• Communication Bit Rate
• Maximum Distance
• Advantage
• LonWorks protocol is media-independent, allowing
  LonWorks devices to communicate over any physical
  transport media.

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Protocol Channel (contd)

• Variety of communications media
• Twisted pair
• Power line
• Radio frequency
• Coaxial cabling
• Fiber optics

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Protocol Media Access Control

• Media Access Control Algorithm
• Randomize their access to media to avoid
  collision
• In back off, randomize over a minimum of 16
  different levels of delay called Beta 2 slots
• The number of available Beta 2 slots is
  dynamically adjustable (16-1008) by each device,
  based on an estimate of the network loading.
• Advantage
• Minimize media access delay with a small of
  Beta 2 slots during periods of light loads
• Sustain performance during periods of heavy loads

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Protocol - Addressing

• Addressing
• Defines how packets are routed from a source to
  one or more destination devices
• LonWorks Provides 4 Types of Addresses
• Every packet transmitted over the LonWorks
  contains a source address and destination
  address, which can be any of the following 4
  addresses.
• Physical Address
• Device Address
• Group Address
• Broadcast Address

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Protocol Addressing (contd)

• Physical Address
• Every device has a unique 48-bit identifier
  called Neuron ID that will not change during the
  life time of this device
• Device Address
• A device is assigned a Device Address when it is
  installed into a particular network.
• Device Address consists of Domain ID, Subset ID
  and Node ID
• Devices must be in the same domain to exchange
  packets
• Multiple domains are used if there exists a
  desire to separate the devices so that they dont
  interoperate
• Group Address
• A group is a logical collection of devices within
  a domain.
• Devices are grouped without regard for their
  physical locations
• Broadcast Address
• Identifies all devices in a subnet or domain

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Protocol Message Services

• Acknowledged Messaging
• When a packet is sent to a device or a group of
  devices, individual acknowledgements are expected
  from each receiver
• Repeated Messaging
• Send a packet multiple times
• Unacknowledged Messaging
• Packet is being sent only once and no response is
  expected
• Unauthenticated Messaging
• Allow the receivers of a message to determine if
  the sender is authorized to send that message
• Prevent unauthenticated access to devices

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Protocol Network Variable

• Network Variable
• Any data item (temperature, a switch value) that
  a particular device application program expects
  to get from other devices or make available to
  other devices
• Network variables must be the same type to be
  connected
• Type translators are available to convert one
  type to another
• Advantage
• With Network variables, the application program
  does not need to know where input variables come
  from and where to put output variables
• During a process in network design and
  installation, the device firmware, implementation
  of LonWorks Protocol inside Neuron Chip, is
  configured to know the corresponding logical
  addresses

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Protocol - Limits

• Devices in a subnet 127
• Subnets in a domain 255
• Devices in a domain 32,385
• Domains in a network 248
• Maximum Devices in System 32K 248
• Members in a group
• Unacknowledged or Repeated No Limit
• Acknowledged or Request Response 63
• Groups in a domain 255
• Channels in a network No Limit
• Bytes in a network variable 31
• Bytes in an application or foreign frame
  message 228
• Bytes in a data file 232

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Protocol - Interoperability

• Interoperability
• Means that multiple devices from the same or
  different manufactures can be integrated into a
  single control network without requiring custom
  nodes or custom programming
• How is Interoperability Assured?
• Most LonWorks devices has a Neuron Chip inside
  and the protocol is available on the Neuron Chip
• LonMARK Interoperability Association, an
  independent body, manages the evolution of
  interoperability mode and certification of
  products that conform to the interoperability
  standard

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Protocol - FAQ

• Is LonWorks Protocol Deterministic?
• MAC algorithm guarantees deterministic response
  for priority message during periods of heavy
  loads
• Is LonWorks Protocol Reliable?
• End-to-end acknowledgements
• All packet transmissions incorporate a 16-bit
  error correction polynomial

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LonWorks Devices
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Neuron Chip

• Neuron Chip
• A semiconductor device specifically designed for
  providing intelligence and networking
  capabilities to low-cost control devices
• Has 3 microprocessors that provide both
  communication and application processing
  abilities
• The name is chosen to point out the similarity
  with human brain
• A complete implementation of LonWorks protocol,
  called Firmware, is contained in the ROM of each
  Neuron Chip

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Transceivers

• Transceivers provide a physical communication
  interface between a LonWorks device and a
  LonWorks network
• It is important to know which transceivers in a
  given product to interoperate directly

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Comparison with CAN Bus

• LonWorks is media-independent
• LonWorks addressing scheme make it ideal for very
  small or large networks without concern about
  exceeding available addressing space
• LonWorks MAC algorithm assures sustained
  performance even during period of heavy loads
• LonWorks multicast addressing guarantees that all
  of the addressed nodes in a group received a
  message while CAN multicast addressing ensures
  only that at least one, but not all, of the nodes
  received a message

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References

• http//www.echelon.com/solutions/Markets/industria
  l/
• Introduction to the LonWorks System
• A LonWorks Overview
• Technology Comparison LonWorks Systems versus
  DeviceNet